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Abstract

In this work, we demonstrate experimentally the use of an array of gold nanodisks on functionalized silicon for chemosensing purposes. The metallic nanostructures are designed to display a very strong plasmonic resonance in the infrared regime, which results in highly sensitive sensing. Unlike usual experiments which are based on the functionalization of the metal surface, we functionalized here the silicon substrate. This silicon surface was modified chemically by buildup of an organosilane self-assembled monolayer (SAM) containing isocyanate as functional group. These groups allow for an easy surface regeneration by simple heating, thanks to the thermally reversible interaction isocyanate-analyte, which allows the cyclic use of the sensor. The technique showed a high sensitivity to surface binding events in gas and allowed the surface regeneration by heating of the sensor at 150°C. A relative wavelength shift ∆λmax/λ0 = 0.027 was obtained when the saturation level was reached.

Figures (5)

Fig. 1 (a) Geometric depiction of four gold nanodisks arranged in a square array on a silicon substrate. (b) Simulated and measured power transmission spectra normalized to the transmittivity of the substrate (c) Top and side views of the simulated electric field magnitude (color) and electric current density inside the metal (arrows) for the designed nanodisks at their resonance frequency, excited with normal incident light whose electric field is polarized along the x-direction. Side view uses a logarithmic scale in the field magnitude. The dashed line in each view indicates the cutplane shown in the other view.

Fig. 4 (a) Transmission spectra at different exposure times to ethylenediamine vapour. (b) Saturation curve showing the resonance shift as a function of exposure time, and fitting to the Langmuir model. The spectrum at 45 min is not shown for the sake of clarity

Fig. 5 Transmission spectra after the functionalization of the silicon surface (black curve), after sensing of ethylenediamine (red curve) and after heating at 150°C (dashed curve). Note that the power transmission levels differs from previous results due to the sample being from a different fabrication run.